How this is done depends entirely on the properties of the superclass. If the colour and position are both protected or private, than you can write directly to the properties of the superclass. If the superclass accepts a colour and position as a part of its constructor, you can chain the subclass to the superclass with
Chances are if you are required to alter the code, than the superclass does not accept parameters (otherwise an overwrite is completely useless since the subclass can just use the superclass constructors), which will lead me to believe that the properties are likely protected. If they are not, you need mutator's in order to set the new colour and position. In either the these two events, you will be overridding the default superclass constructor.
header('HTTP/1.1 420 Enhance Your Calm');